What is the value of the slope of a graph obtained by plotting the concentration of reactant $(A)_t$ versus time for zero order reaction?

For a zero order reaction, the rate of reaction is independent of the concentration of the reactant.

The integrated rate equation for a zero order reaction is given by:

$[A]_t = -kt + [A]_0$

where $[A]_t$ is the concentration of the reactant at time $t$, $[A]_0$ is the initial concentration, and $k$ is the rate constant.

Comparing this equation with the equation of a straight line $y = mx + c$, we get:

$y = [A]_t$

$x = t$

$m = -k$

$c = [A]_0$

Thus, plotting the concentration of reactant $[A]_t$ versus time $t$ yields a straight line with a slope of $-k$.

Answer: $-k$